During the laser cutting of metal workpieces, a laser beam is focused onto the workpiece which is to be cut. Often, a cutting gas is simultaneously blown onto the cutting location by means of a nozzle. The cutting gas is intended to protect the nozzle of the cutting installation and the focusing lens contained therein from metal spatter and slag formed during the cutting process and, at the same time, to assist with flushing the molten material and the slag out of the cutting kerf. In many cases, the cutting gas used is oxygen or an oxygen-containing gas mixture. The chemical reaction of the oxygen with the cut material (for example steel) produces additional heat which assists the cutting process. Steel combustion then takes place.
During laser cutting, the person skilled in the art distinguishes between conventional laser cutting with a cutting speed of at most 10 m/min and high-speed cutting of thin metal sheets with cutting speeds of up to 100 m/min (Prei.beta.ig et al., High speed laser cutting of thin metal sheets, SPIE Vol. 2207, 96-110). In connection with high-speed cutting of thin metal sheets, it is already known from DE-A-4,123,716 to use a mixture of inert gas and hydrogen as the cutting gas. During high-speed cutting, the cutting speed is limited by so-called melt build-up phenomena. The high viscosity of the molten material which is formed during cutting limits the speed which can be achieved. DE-A4,123,716 teaches the person skilled in the art that the addition of hydrogen to the cutting gas reduces the surface tension of the molten material, thus counteracting a build-up thereof.